Based on the pile active underpinning project of Xima Bridge in Fuzhou Metro Line I shield tunnel

considering the complex hyperstatic structures composed by bridge superstructure

bridge piles and soil masses

the numerical simulation and the field monitoring data are utilized jointly to study the inner force and displacement responses of hyperstatic structures under different jacking loads. The influences of superstructure stiffness and substructure stiffness on the determination of jacking load are emphasized. The reasonable jacking loads for two typical conditions (the piles under cap beam and abutment beam) are 1 800 kN and 2 600 kN respectively

which make the axial forces of underpinned piles reduce to zero. The field monitoring is also carried out during construction

and the displacement of bridge superstructure and the axial force of bridge pile from monitoring data are consistent with their counterparts from numerical simulations. Based on these results from numerical simulation and field monitoring

a simplified analytical method is further proposed to calculate the reasonable active jacking load by considering the stiffness ratio between the superstructure and substructure

which can provide some reference for the pile underpinning projects under similar scenarios.